To find the peak flavor of freshly roasted coffee, one needs to balance two important factors: the loss of aromatics, and the build-up of carbon dioxide. For most coffees, this happens in a window of 4-14 days after roasting.
It's well known that if you want the best cup of coffee, you have to use fresh, quality beans. But what does fresh coffee really mean? More importantly, how do you bring the best flavor out of your favorite coffees?
You may have noticed that "fresh coffee" can take on a wholly different meaning depending on who you're asking. This is because "fresh" often functions as shorthand for roasters; generally, it means when a roaster feels their coffee tastes its best. For most, this is not as soon as the coffee comes out of the roaster. To better understand freshness and flavor, it's important to think about where coffee's flavors are formed.
While much of a coffee's distinctive qualities are determined by where it's grown and how it's processed, the bulk of coffee flavor comes from roasting. If you've had the chance to take in the smell of unroasted or green coffee, you'll recall how the aroma more closely resembles fresh produce and green peppers than a fresh brewed cuppa. That warm, deeply sweet smell of a newly opened bag of coffee? It's the product of artisan roasting. Roasting is also the chief culprit behind coffee going stale. During the roasting process, the beans lose mass and become more porous, making it easier for aromatics to escape the coffee. Easier to smell and enjoy. Easier to lose.
According to Professor Chahan Yeretzian, the head of the Coffee Excellence Center at the Zurich University of Applied Science, "The aroma of the roasted bean... if you measure it, you see a loss of freshness between a few days, even one day."
But, in the pursuit of peak flavor, there is more than aroma to consider. The immense heat of roasting breaks down sugars and amino acids into carbon dioxide. In the first few days, the build-up of CO2 can significantly affect brewing, making it much harder to get a tasty cup. The coffee has to rest and degas before it becomes easy to brew. From Professor Yeretzian, "In the first week, [the coffee] evolves every day... from a CO2 perspective the first week is quite dynamic. I wouldn't think of it as aging; it's more a calming down." For coffee lovers seeking the most flavor, you should aim to balance the degassing of CO2 with the loss of important aromatics. For darker roasted coffees, this period usually starts after the first few days after roasting*. For lighter roasted coffees, it's a good idea to wait a little longer before diving in, say 5-10 days. This is because dark roast coffees are more porous than light roast after spending more time in the roaster.
Source: Boot Camp Coffee
It's important to consider how you'll be enjoying your coffee as well. For more gentle brew methods like drip or pour over, you can start using your favorite coffees a little earlier. For espresso, it's important to give the coffee a bit more time to rest before subjecting it to an intense, pressurized brewing environment. *Something to consider: a very dark roasted coffee will have oils on the surface of the beans. This exposure of the coffee oils to air leads to fast oxidation of those oils, which can cause rancid flavors. Another good reason to not wait to brew your favorite dark roast.
Greater Goods take on their coffee
"For our coffees, we roast them in a low oxygen environment (Loring roasters are closed systems) and all of our bags are nitrogen flushed and sealed for less than 1% residual oxygen and fitted with one-way valves allowing the CO2 to escape during the phase when the coffee is degassing. We've blindly cupped (sensory evaluated) coffees packaged in this low oxygen environment that were roasted 90 days before against the same coffee roasted 24 hours before and while a difference could be detected, there was not a very large delta between the two when scoring using the SCAA protocol. Aroma, flavor, acidity and sweetness are retained. However, aroma and flavor degradation is noticeable with coffees this old when stored in an environment of even 2%+ oxygen and very noticeable when stored in 20-21% oxygen (normal air).
For any coffees prepared as an espresso, we recommend waiting at least 5 days after the roast date before using. Our internal standard is between 7-11 days before use as espresso. For drip/pour-over, we wait 4-7 days. For cold brew, 10-14 days. The "sweet spot" varies according to coffee roast degree (light/dark), bean density, physical size, processing method and even the varietal(s)."
Sterling Roasters and their coffee
Aric Miller of Sterling Roasters weighed in on this as well. As you may know, Sterling makes our Clive exclusive Lovejoy Blend. "Coffee 'freshness' is a fickle thing. In the industry, we all know that super fresh coffee is not good. The beans need time to off-gas the latent carbon dioxide. The carbon dioxide translates to carbonic acid in the cup which is astringent as all get out. So, how long should we rest the beans? What is the shelf life of coffee with the current lighter roast profiles? Here at Clive, we let our drip coffees rest at least 7 days and our espressos the same.
Over the course of the last few months, I have conducted a battery of tests using coffees with age ranges from 1 day off roast to 1 1/2 years off roast. The tests were all done blind and all done to taste, no scientific equipment (refractometer et al) was used. The results were startling and made me reconsider my definition of peak freshness. As expected, the coffees that were in the 7-21 day range were delicious. The real surprise, however, were the coffees at a month, 2 months+. Only, after about 3 months did we notice a truly discernible loss of what I would call vibrancy. The coffees still tasted just fine, but had lost the higher acid notes that constitute a balanced cup. Hell, the 6-month tasted fine too. It wasn't until the year and a half coffee that it was completely evident that the coffee was old. There was no bloom on the brew and the taste, while still oddly sweet, was lifeless. I think it's high time to start reevaluating the lifespan and sweet spot of coffee. We've had espresso in house that has been as far off roast as 27 days and it was still phenomenal. Different, but great. So, against our better judgment, we didn't pull it. Then, at 28 days it simply fell apart. Go figure.
Anyway, I'm always learning and trying to unlearn what I think I know about coffee. It's ever changing and I think we all owe it to ourselves to be open to that change. Just think about how different things are now than even a couple of years ago, and let go of preconceptions."
Here at Clive, we take freshness seriously. We only offer coffees that have a roast date on the bag.
Other reading: Sprudge interview with Prof. Chahan Yeretzian – 9/23/2015 and What is the Shelf Life of Roasted Coffee? A Literature Review on Coffee Staling Emma Sage, Coffee Science Manager, SCAA – SCAA Chronicle 2/15/2012
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